Flu activity is picking up around the country and is expected to keep increasing over the coming weeks.

“This year so far the most common strain of influenza circulating is influenza A, H3N2,” said Dr. Nancy Messonnier, director of the National Center for Immunization and Respiratory Diseases.

The strain is known to cause more severe illness, especially in young children and people 65 and older.

According to the latest data from the CDC, in the last week of 2016, 10 states around the U.S. were experiencing high levels of flu-like activity: Alabama, Georgia, Louisiana, Missouri, New Jersey, New York, Oklahoma, Oregon, South Carolina, and Utah. High levels were also reported in New York City and Puerto Rico.

In 10 other states — Arizona, Illinois, Indiana, Kentucky, Minnesota, Mississippi, Nevada, North Carolina, Pennsylvania, and Virginia — flu-like activity was reported to be moderate.

Nationwide, the CDC reports that since October 1, more than 1,300 people have been hospitalized due to laboratory-confirmed cases of flu. Officials say they expect the numbers to keep increasing across the country over the next several weeks.

Dr. Janette Nesheiwat of CityMD in New York City said she’s seen a lot of patients with the flu over the last few weeks.

“In my last shift, I diagnosed about 10 cases in a single day of influenza A,” she told CBS News. “And that’s just me at this one site.”

But while doctors are seeing a rise in flu cases right now, they say the numbers appear to be in line with previous seasons.

The CDC says so far this year’s flu shot seems to be well matched against the prevalent strains out there.

“Influenza vaccine can protect you against illness,” Messonier said. “It also can protect you from hospitalization.”